This in vitro study compared surface roughness (Ra) and CIEDE2000 color change (ΔE00) of two giomer flowables with surface pre-reacted glass-ionomer (S-PRG) filler, Beautifil Flow Plus F00 and Beautifil Flow Plus X F00, and two nanofill resin composites, Filtek Supreme Ultra Flowable and the packable Filtek Supreme Ultra Universal, during simulated toothbrushing. Ten discs per material were cured against glass without finishing or polishing and brushed for 10,000 linear cycles at 2.5 N. Ra and color were measured at baseline and every 2500 cycles; scanning electron microscopy illustrated the surfaces. Beautifil Flow Plus X became smoother after the first 2500 cycles (p ≤ 0.001), and no material became significantly rougher. At 10,000 cycles, Filtek Supreme Ultra Universal was rougher than the three flowables. ΔE00 differed among materials (p < 0.001) but not between intervals; Beautifil Flow Plus X changed the least (mean 0.408), less than Beautifil Flow Plus (0.886) and Filtek Supreme Ultra Universal (0.768), and no disc reached the 50:50% acceptability threshold of 1.8. Without an unbrushed control, ΔE00 reflects brushing, storage, and measurement combined. Under this protocol, Beautifil Flow Plus X became smoother and changed color the least.