We studied the effects of chemical pressure on Gd1-yRyMn0.7Co0.3O3 (R = nonmagnetic rare-earth element) with y = 0.1, 0.3, and 0.5. The substitution of Gd with La, Y, or Lu in orthorhombic Gd1-yRyMn1-xCoxO3 induced a systematic change in the unit-cell volume. Our results reveal that increasing or decreasing the average ionic radius of the rare-earth element in the compound affects the magnetic ordering temperature T-C. The reduction in the proportion of Gd owing to substitution by nonmagnetic elements weakens the spin reversal effect.