The lattice, magnetic and superconducting properties of the oxides, (La1-xMx)2CuO4-y (M=Ba,Ca), were extensively investigated as a function of both temperature T and Ba-concentration x. For x > 0.025 the compounds show a superconducting transition, with which two different types of phase transitions were found to compete in the T-x plane; crystal distortion from a tetragonal to an orthorhombic lattice and antiferromagnetic ordering. External hydrostatic pressure tends to depress the magnetic ordering and to enhance superconductivity.