When Oxenaar takes over from Hammacher on 1 July 1963, he is 37 years old and one of Europe’s youngest museum directors. A month after his appointment, the Algemeen Dagblad newspaper runs the headline: ‘Kröller-Müller Museum in adept young hands’. Oxenaar intends to continue the policy line of his predecessors for the time being, but also to implement changes. He envisions major projects to strengthen the basic facilities around the collection. Accordingly, he quickly pursues a second extension of the sculpture garden, to facilitate the continued growth of the sculpture collection. Oxenaar also wants to make efforts to ‘invigorate the international contacts’.

After obtaining his doctorate, a condition for his directorship, Oxenaar begins a PhD study on Bart van der Leck. Therefore, to support his successor Hammacher remains involved in the expansion of the sculpture garden and advises on the acquisition of sculptures. Oxenaar benefits from Hammacher’s commitment and his international network, but also feels his freedom as the new director somewhat restricted. The new acquisitions in 1963, including sculptures by Barbara Hepworth, Frits Wotruba, Zoltan Kemeny and Joseph Csáky, testify to a continuation of Hammacher’s policy. Oxenaar has yet to introduce any new artists to the collection.

In the annual report, Oxenaar dedicates no fewer than four pages to the ‘necessary improvement’ of the now outdated building by Henry van de Velde. The condition is worrying: damp spots, cracks and other wear and tear on the interior and exterior. Since taking office, Oxenaar has managed to implement some urgent alterations: the lighting in the museum has been modernized and the number of telephone lines increased – this was essential because until then the museum had only one outside line. But there is still no alarm system. ‘For the time being, the security situation, which is already a serious problem given the remote location, will thus remain highly unsatisfactory.’ There is also a shortage of office and storage space for the responsible storage of the ever-growing collection.

Oxenaar’s argument is effective. Later that year he can report that discussions with the Chief Government Architect have led to a ‘yet to be defined’ plan to build a new wing for the museum. ‘On the other hand, such a plan is so far-reaching, time-consuming and costly that its realization will likely take years. It will therefore be necessary to implement some interim provisions.’

Oxenaar attaches great importance to the relationship with private collectors. ‘The private [...] can be more adventurous, as they have no obligations to the community. They do not have to give an overall, balanced picture of modern art, as a museum does. It is therefore only natural that a contact between a private individual and a museum works so well.’ This often results in major loans for exhibitions, but also leads to donations of high-profile works of art that the museum itself cannot purchase.

In this way the museum receives two 15^th century gravestones from a foundation set up by the New York collector Joost Meerloo, the aim of which is to ‘find works in America of Asian, Old American or primitive cultures, which are underrepresented or entirely absent in Dutch museums’. Baron Philippe Lambert donates Standing woman (1947) by Frits Wotruba, in memory of his mother Baroness Lambert, a good friend of Henry van de Velde. ‘She regarded this donation partly as a homage to their friendship.’

To commemorate Van de Velde's hundredth birthday (3 April 1963), the museum together with the Belgian Van de Velde Society organizes a retrospective of his multifaceted oeuvre: paintings, drawings, prints, book bindings, posters, illustrations, furniture, textile designs, jewellery, utensils and industrial designs. For Oxenaar, it is 'a privilege and a great experience to be able to provide an insight into the work of the artist who realized so many of Mrs Kröller-Müller ideas, in a building of his own design, using the many objects that he created and the museum now possesses’.

In May 1964, Gerrit Rietveld visits the sculpture garden to find a suitable location for his Sonsbeek pavilion. On that occasion, he expresses the wish for 'the pavilion to be completely rebuilt in its original form'. Unfortunately, Rietveld dies a month later. Now that the architect can no longer provide instructions, that responsibility lies with the contractors L. de Vries from Arnhem, which also built the original pavilion with some of the same workers. The pavilion is carefully reconstructed on the basis of photographs and with the support of the board members of the Sonsbeek '49 Foundation.

The summer of 1964 is devoted to a retrospective of the work of the Paris-based French-Argentinian sculptor Alicia Penalba. In the museum and sculpture garden, 50 of her largely bronze sculptures are shown, including Relief. After Otterlo, the exhibition travels to the Van Abbe Museum in Eindhoven and then on to Germany. Oxenaar acquires Relief, which consists of 16 elements of gold-plated polyester. Under Penalba’s supervision, the elements are attached to the outer wall of the museum. But problems with the adhesive layer soon arise, causing the gold plating to become detached. Within a year the work is no longer presentable. Penalba is asked to make a second version, but that too proves to be no match for the outdoors. Eventually it is decided to exhibit the relief permanently inside.

Oxenaar has managed to acquire Henry Moore’s Three Upright Motives and the sculpture group is festively unveiled on 10 April 1965. Ellen Joosten does the honours, because Oxenaar has to rest for a month following a car accident. After the opening by Hendrik Jan Reinink, the film A sculptor’s landscape by John Read is screened, which examines Moore’s oeuvre in relation to the landscape. In the annual report, Oxenaar writes that Otterlo is now the only place in Europe where ‘the three sculptures, which constitute an inseparable whole for Moore, can actually be seen together’.

In May 1965, the Rietveld pavilion is opened with a retrospective of the work of Barbara Hepworth. First the pavilion is officially 'handed over' to the museum. Willem van Tijen, initiator and friend of the architect, gives a short speech and Bep Eskes-Rietveld speaks about her father and thanks everyone on behalf of the family. After the handover, Hepworth's exhibition is opened by the ambassador of Great Britain and Northern Ireland in the presence of the artist. Hammacher presents a contemplation on Hepworth’s work.

In the annual report, Oxenaar once again appeals for a necessary expansion of the museum. ‘Now, after more than 27 years, it is all too clear that it was indeed built temporarily in 1938.’ The number of visitors has risen 100% in 10 years, partly due to the increasing reputation of the sculpture garden and the arrival of the Rietveld pavilion. ‘There is thus every reason to protect the building from decay and major changes. The insights regarding the urgently required expansion [...] are therefore definitely leaning towards the construction of a new wing, which might connect via a glass corridor to the existing building, which can then remain completely intact.’