This work focused on the selection of suitable mullite-based matrix materials for all-oxide ceramic matrix composites. Through monolithic characterization, data points for the He-Hutchinson model were generated, and conclusions were drawn regarding the potential damage-tolerant behavior of the composites (Figure 1). Various matrix compositions with different coarse and fine fractions were fabricated by slip casting, allowing a more detailed investigation of the influence of different powders and particle sizes. Monolithic samples were characterized using the impulse excitation technique to determine the Young´s modulus, as well as an adapted single-edge V-notch beam (SEVNB) test to analyse the fracture energy. In addition to monolithic samples, all-oxide ceramic matrix composites with the same matrix material were investigated to validate the conclusions drawn from the monolithic specimens. The composite specimens were manufactured using a prepreg process with the same powder compositions as for monolithic samples with subsequent infiltration of NextelTM 720 fabrics. These specimens were tested by a three-point flexural test. The results obtained from the monolithic samples were in excellent agreement with the failure behavior of the composites. The mullite/mullite samples reached flexural strengths of up to 158 MPa, which are comparable to values reported by previous studies [1,2]. The generated data enabled a selection of suitable matrix materials for use in composites. This is intended to support the development of all-oxide ceramic matrix composites with high strength and damage tolerance, while contributing to a reduction in research costs for new material systems [3].